There is known packaging in existence for housing replacement sensor crystals that are to be used in vacuum deposition processing apparatus, such as for optical coating applications. These crystals are thin disc-like quartz elements that are incorporated into a sensor assembly which can be disposed within or otherwise provided relative to a vacuum deposition chamber. The crystals are manufactured with a circularly shaped active region in the center of the crystal which upon placement into the sensor assembly can be resonated upon application of a proper voltage. This resonance can be used to determine the rate and thickness of deposition in the chamber and hence wafer thickness. Due to the exposure environment, it is expected that these crystals, on occasion, must be replaced. To that end, crystal sensor assemblies are constructed to permit replacement of used or worn sensors.
Referring to FIG. 1, a first prior art replacement crystal package 100 includes a box-like enclosure 104 that is sized to store a predetermined number of crystals 36, the crystals being separated from one another in the stacked arrangement by a series of alternating static-free paper inserts 112 that sandwich each crystal. In order to remove a crystal 36 from the package 100, the box-like enclosure 104 must first be opened and then a paper insert 112 must be removed prior to removing a crystal therefrom, usually with tweezers (not shown). This particular package design has a number of disadvantages. First, a storage system as described in FIG. 1 is expensive to manufacture as well as highly labor intensive. Second and perhaps more significantly, each of the crystals 36 are evenly supported, including their sensitive center regions 42, on the paper inserts 112, potentially subjecting the crystals to damage prior to their use.
Referring to FIG. 2, a second prior art crystal package 120 is depicted. In this particular package design, a plurality of crystals 36 are horizontally supported within a plurality of spaced recesses 128 that are disposed about the outer periphery of a plastic-molded tray portion 132. A transparent cover 136 is placed in overlaying relation to the tray portion 132, the cover including a single opening 140 that can be aligned, through rotation of the cover, with one of the spaced recesses 128.
Rotation of the cover 136 permits removal of a crystal 36 by means of tweezers (not shown) that can engage the edges of a crystal or removal can be alternatively effected by “flipping” the package 120 and permitting a stored crystal to fall through the aligned cover opening 140.
A number of disadvantages are also found using this latter crystal package design. First, the recesses 128 are constructed to evenly support each crystal 36, as in the first instance, including the active center area 42 which is therefore essentially unprotected during storage. Second, it is possible that any or all of the stored crystals 36 can be dislodged prematurely from any one of the recesses 128. Subsequently, the dislodged crystal(s) can become wedged between the cover 136 and the tray portion 132 when the cover is rotated or when the package 120 is tipped for removal of a crystal 36, causing possible damage to a crystal or otherwise preventing the crystal from being removed, without a certain degree of manipulation or by destroying the package 120.